This visualization uses an area chart to show the relationship between study hours and the corresponding grade values (A=4, B=3, C=2, D=1) for individual students. The chart’s fill uses a linear gradient transitioning from rose to blue to green. The code loads a CSV from GitHub, filters for entries with study hours and grades, maps letters to numeric values, and sorts the data by study hours before creating a smooth monotone-X curve. The axes are drawn with `d3.axisBottom` and `d3.axisLeft`.